The White House asked the U.S. Congress for $3.7 billion in emergency spending on Tuesday to address a cross-border surge of children from Central America that is taxing public resources and causing a political headache for President Barack Obama.

It was Obama's most substantive response to date as he struggles to gain control of a humanitarian crisis along the Texas border with Mexico. The money would both pay to care for the children and accelerate a return to their home countries.

The funding move will test Obama's ability to negotiate effectively with Republican lawmakers who have blocked much of his agenda ahead of a November election when they hope to capture the U.S. Senate.

Obama has vowed to swiftly return to their home countries the tens of thousands of children under 18 who have flocked to the United States in recent months. Many who flee are escaping extreme poverty, gangs and drug violence.

He risks the wrath of Latino allies in the United States who are looking to him to act on his own to loosen, not strengthen, immigration rules.

Seeking to make the request more politically acceptable to lawmakers, the White House added $615 million in urgently needed money to help fight summer wildfires that have been raging in western states.

This brought the total funding request to $4.315 billion, a figure that some Republicans might find difficult to swallow without budget cuts elsewhere.

Due to leave on a Democratic Party fundraising trip to Colorado and Texas, Obama has offered to meet while in Texas with the border state's Republican governor, Rick Perry, who has criticized Obama's refusal to visit the border.

White House officials who briefed reporters said the largest portion, $1.8 billion, would go to the U.S. Health and Human Services Department to provide appropriate care for the children while in U.S. custody.

The United Sates provides assistance to the Central American countries. Why do we have to provide more to those who think living in the US is their right? I really do have a soft spot in my heart for the children that were sent here without an adult, but enough is enough. If they are allowed to...

Without this money, "HHS will be unable to address the influx of children by securing sufficient shelter capacity with the number of children held at Border Patrol stations continuing to increase, for longer periods of time," the White House said.

Another $1.1 billion would go to the U.S. Homeland Security Department to pay for transporting the children, expanding investigations of immigrant smugglers and pay for the detention and removal of undocumented adults traveling with children.

In addition, $433 million would go toward stepping up border enforcement, including an increase in air surveillance. The U.S. Justice Department would receive $64 million to hire about 40 additional immigration judges to reduce the backlog of cases that is slowing the process of deportation.

Finally, $300 million would go to the State Department to pay for repatriating and reintegrating migrants back into their home countries and "help the governments in the region better control their borders," the White House said.

SENDING CHILDREN HOME

The United States plans to give priority to child migrants over adults in deportation hearings as part of a broader initiative to deal with a surge of unaccompanied minors crossing the border illegally, a Justice Department official told Reuters.

The new policy, to be announced by the Justice Department on Wednesday, is one of several steps the administration is taking to accelerate the removal of tens of thousands of child migrants entering the United States, many from Central America.

The official gave few details of how quickly the "removal" hearings would proceed, but the White House asked Congress on Tuesday for $45 million to hire 40 judges to address backlogs in courts that mean deportation hearings often take more than 18 months.

Immigration courts typically prioritize immigrants held in detention for hearings, but under U.S. law, children are not detained. The policy change means the courts will now hear first from newly arrived children, while adult immigrants not in detention, including those who are seeking asylum, will have to wait longer, the official said.

As many as 90,000 children may cross into the United States this year, according to U.S. government estimates. They are mainly from Guatemala, El Salvador and Honduras, where gang violence has led them to make dangerous journeys to escape.

The United States is facing budget strains over the cost of providing food, shelter and medical care for the children, and President Barack Obama has said most of the children will be sent home.

But the influx of children has created the largest ever backlog in immigration courts. In the first half of the year, there were 366,724 pending cases, the highest on record, according to Justice Department data.

As of March, the average wait time for a case was 578 days, according to Justice Department records obtained by the Transactional Records Access Clearinghouse, a data-gathering organization.

The Justice Department declined to give an estimate for the expected wait times under the new policy to be announced on Wednesday.

GANG VIOLENCE NO EXCUSE

Total processing times will vary based on the complexity of the case, said Lauren Alder Reid, a lawyer who handles immigration at the Justice Department.

Reid said there are many forms of protection to which the children are entitled to apply and judges will determine whether their circumstances merit relief from deportation.

Evaluating each case can be a lengthy process. Domestic abuse, for example, is grounds for relief and requires U.S. officials to interview relatives and neighbors of children.

But the law does not grant relief based on gang violence, which human rights advocates blame most for driving the children out of their home countries.

Republicans have blamed the crisis on Obama's 2012 policy that delayed deportations for children brought into the United States illegally by their parents.

The White House has acknowledged that there has been misinformation about U.S. policy. Obama has sought to spread the message that if children come to the United States illegally they will be sent back. But that message has been complicated by the fact that it can take a year or more to deport children.

The White House wants Congress to change an anti-trafficking law that requires lengthy deportation proceedings for most children.

Under the 2008 law, children entering the United States illegally from countries outside of Mexico and Canada must go through immigration courts before they can be deported. Obama is seeking greater flexibility in the law to allow faster deportation of children from countries that do not border the United States.

The immigrants could then be repatriated based on a border agent's evaluation within 48 hours of being caught.

Miguel Hernandez, right, an immigrant rights activist, stands among anti-immigration activists outside of the U.S. Border Patrol Murrieta Station in Murrieta, California. Immigration protesters have staged rallies in front of the station for about a week in response to a wave of undocumented...